Pediatric Acute Gvhd: Transcriptome Analysis of Gastrointestinal Biopsies Reveal a Unique Signature in Pediatric Acute GI Gvhd with Involvement of the ERK Pathway and Similarities with Pediatric Inflammatory Bowel Disease

Abstract

<h3>Introduction</h3> Studies of target organs at the time of acute graft versus host disease (GVHD) are needed to identify novel inflammatory and regulatory pathways. <h3>Methods</h3> We performed a prospective transcriptome analysis of gastrointestinal (GI) biopsies at diagnosis of acute GI GVHD and compared these to bone marrow transplant (BMT) patients without GVHD. Allogeneic BMT patients ≥2 years old undergoing endoscopy for clinical indications had 2 additional rectosigmoid mucosal biopsies for transcriptome analysis. Transcriptome data from 211 ulcerative colitis (UC) patients were included to uncover genes and pathways shared between GVHD and UC. Rectal biopsies from 20 children without inflammatory bowel disease (IBD) served as controls. <h3>Results</h3> Twenty-one patients underwent endoscopy pre (n=5) or post BMT (n=16). Median age of patients was 13.5 years (range 4.5 -25 years). Four patients were excluded from analyses (pre BMT colitis n=3, no lower GI biopsy n=1). Nine patients had acute GI GVHD, while 8 patients did not (Table 1). Principal component analysis shows patient clustering of those with and without GVHD, suggesting distinct transcriptomic mechanisms driving disease (Figure 1A). We identified 1310 significant genes, 144 of which were downregulated and 1266 upregulated in acute GVHD compared to no GVHD (Figure 1B). Top upregulated biological processes in GVHD revealed an innate antimicrobial response and associated cytokine signaling, notable for interferons. Top 20 differentially expressed genes in acute GVHD (Table 2), include CXCL9, CXCL10 and CXCL11, which are chemokines involved in GVHD, and IDO1 which regulates tryptophan metabolism. Four hundred and ninety shared genes were upregulated, and 126 genes were downregulated in GVHD and UC. Notable shared downregulated pathways involved butyrate metabolism (Table 3). DUOXA2, a gene involved in regulating innate antimicrobial responses in IBD, was the top upregulated genes in pediatric IBD and was the second highest differentially expressed gene in the acute GVHD, providing additional rationale for intestinal microbiome modulation in both diseases. Genes involving the ERK1/2 cascade (Table 4) were upregulated in acute GVHD (p=1.67 × 10 ⁻³) providing rationale for exploring ERK1/2 inhibition as novel acute GVHD treatment. <h3>Conclusions</h3> Acute GI GVHD has a distinct transcriptome signature which includes pathways of innate antimicrobial responses highlighting the role for microbiome modulation. The ERK1/2 cascade pathway is upregulated, suggesting a novel target in acute GI GVHD. Acute GI GVHD has important similarities with the UC transcriptome, including upregulation of DUOXA2 and downregulation in butyrate metabolism in both.